REPTILE. 



that of birds, and being of course the true clavicle. 

 It should seem, therefore, that footed reptiles which 

 have not this furcal bone are really without clavicles. 

 This agrees with the style of their action. We have 

 shown, see art. MAMMALIA, that the possession of a 

 clavicle, though it is favourable to the cross motion 

 of the anterior extremities, is always a drag upon 

 their efficiency in walking, though not necessarily 

 in leaping, as the spring is then taken from the hind 

 legs. Now, while some of the other Sattria run with 

 no inconsiderable degree of celerity, the tortoise with 

 its clavicles forming a distinct furcal bone, ia one of 

 the slowest of walkers. 



This coincidence between the shoulder of a reptile 

 and that of a bird, in the fact of both having coracoid 

 bones, is a very curious matter ; the curiosity of it is 

 still further increased when we consider that the tor- 

 toises have the shoulder articulated very much like 

 that of a bird, by the support of all the three bones ; 

 and these coincidences become still more interesting 

 when we find that they are greatest in those cases 

 where the mode of production in the reptile resem- 

 bles most nearly that of a bird. 



In the shoulder of the turtle, the bone which an- 

 swers to the scapula or blade-bone, is united by 

 cartilage to the first rudiment of a rib, from which it 

 extends to the shoulder joint. The coracoid extends 

 from the breast-plate to the same ; and the third, or 

 furcal bone, extends backwards below the viscera 

 as far back as the abdomen. These bones form an 

 opening for the windpipe and gullet in the same way 

 as in birds ; and they may be thus compared to the 

 shoulder of a bird, inside the principal supports of 

 the body, and not outside as the bird has them. 



The anterior extremities consist of an arm, a fore- 

 arm, and a hand or paw, as in the mammalia. The 

 arm consists of only one bone, the humerus, as in 

 these. The fore- arm consists of two bones, except in 

 the frogs and toads ; and the hand, and also the plane 

 of the principal articulations of the whole number, 

 are varied to suit the purposes which they are in- 

 tended to serve. In the aquatic tortoises, or turtles, 

 the joints are formed for the motions required in 

 swimming only ; and the paw, though internally com- 

 posed of many bones, is entire externally, so as to be 

 a swimming paw or paddle. In the Scturia the hands 

 have a number of divided toes varying from five to 

 one^mly, variously armed with claws, and capable of 

 most of the motions to which feet with divided toes 

 are applicable,; but, in their general appearance, 

 they may be said to be intermediate between the 

 feet of mammalia and those of birds. The feet 

 which they most resemble are those of the marsupial 

 mammalia. 



The pelvis, which is the base of insertion for the 

 hind legs, is of considerable size ; and the bones of it, 

 contrary to what exists in the mammalia, are move- 

 able on the spinal column, instead of being soldered 

 to it with little or no power of motion. It is this 

 which makes the hind legs appear to be only ap- 

 pendages, and the tail the real continuation of the 

 body ; and this appears the more from the thickness 

 of the basal part of the tail in many of the Species. 

 But even in the frogs, which have no tails, the hind 

 legs still have the appearance of appendages ; and in 

 the best-limbed of the race, there is always a sugges- 

 tion of the footless reptile. The femur or thigh-bone is 

 curved so as to bend backwards at its upper part and 

 forward at its under, something like the letter S. 



There are two fore bones in the leg in most genera ; 

 but in the frogs they are soldered together. The 

 bones of the hind feet are like those of the fore, 

 and, like those, adapted to the peculiar kind of mo- 

 tion which the habit of each requires it to perform. 

 The muscles on the legs of frogs form a sort of calf. 



In the positions of rest and style of motion, there 

 are great diversities. Water-turtles stand on the 

 breast-plate as much as on the legs ; land tortoises 

 stand on the legs ; frogs and toads sit with the axis 

 of the body oblique, and supported anteriorly on the 

 fore legs ; and those saurians which approach the 

 nearest to the serpents have the power of coiling 

 themselves up when they are in a state of repose. 

 Turtles shuflle along, but do not walk ; tortoises walk 

 slowly ; the saurians are walkers, leapers, or climbers, 

 according to the nature of their haunts and their mode 

 of obtaining their food ; and none but the dragons 

 can fly, and their apparent organs of flight are mere 

 parachutes, which protract their fall, and not wings 

 that can gain new motion from the air as a fulcrum 

 or starting-point of resistance. 



In these few remarks, we have made no allusion to 

 the structure and motions of the serpents or ophidian 

 reptiles, because they have little in common with 

 animals having limbs, and therefore it will conduce 

 to the clearness of our brief view of the class if we 

 take them by themselves. We shall therefore notice 

 the remaining points relative to the others. 



Considered with regard to .sensation reptiles iiave 

 even less brain in proportion than they have cranium, 

 and the little they have is very imperfectly developed. 

 They cannot theretbre have much of what may be 

 called internal excitement, that is, of originating ac- 

 tion with very little impulse from without. But, by 

 wanting this, they are left the more exposed to the 

 influence of external causes. This is what keeps 

 them more to certain latitudes and localities than 

 any other animals ; and in respect of the weather in 

 changeable climates, they are excellent weather- 

 gauges in all places where they will live exposed to 

 the weather. 



In respect of quantity of brain there are, however, 

 great differences : the brain of a turtle is not supposed 

 to be above a six thousandth part of the whole, 

 while that of a frog is more than a two hundredth 

 part. The frog should, therefore, be an animal 

 of much greater resource, and it may be on this 

 account that it lives in a greater variety of climates. 



Though the muscles of reptiles have great irrita- 

 bility, and this continues a long time after death, it 

 does not appear that they have much of what is 

 properly called sensibility ; and that their motions 

 and the effects of external impressions on them are 

 much less productive of pleasure or pain than those 

 of mammalia and birds. They have some of the 

 organs of local sense well developed, and others very 

 imperfect. 



Of their touch, or feeling, or general muscular 

 sense, it is difficult to judge, because it cannot be 

 separated from the irritation produced by the mere 

 contractibility of the muscles. Sight appears to be 

 their most perfect local sense. The eyes in most are 

 well-formed and ready in use. The turtles, some of 

 the Sauria, and the frogs, have the eyes supported by 

 bony plates on the anterior part of the sclerotic coat, 

 and this is seldom found in eyes which are not 

 intended for quick and steady vision. The iris of the 

 eve varies in colour, though less than in most of the 



